best short-barrel cartridge in a .308-length rifle?

First off, about the only "benefit" I see for a 16" shorty is "More noise!" or "Let's get LOUD!"

The .308 performs pretty well with a barrel in the 18" to 22" range. My .243 has done quite well on Bambi and prairie dogs with its 19" barrel.

FWIW, in the common loadings, a 7mm08 is a .308 with ten grains weight less bullet. (I prefer the 7mm08 over the .308 from an aesthetics standpoint, but I'm a bit weird that way. )

It is a general truth that the bigger the charge, i.e. the more "powerful" the load, the more velocity/energy/momentum you'll get out of it at any barrel length.

As an example, there are special short-barrel loadings out now for various compact/snubby pistols and revolvers, and for years folks have made loads they believed worked better in the short guns.

However, the truth is a .357 magnum loaded with a max charge of H110 (for example) makes more power and velocity out of a snubby revolver than does any "short-barrel load" of a faster powder. Similarly, a .300 Weatherby Magnum fired out of a 16" barrel is going to out-perform a .300 Win Mag, which will beat a .308, which will beat a .300 Whisper, which will beat a .30 Carbine fired out of a 16" barrel.

That doesn't really appeal to most folks, though, because the shorter barrel will greatly amplify the blast/concussion and flash of the heavier round. And there is (at least a perception of) more loss of velocity and energy between what that monster round would have produced from a full-length barrel and the less impressive numbers when fired through the 16" tube.

So, it may be uncomfortable to shoot, may "waste" a whole lot of powder, may burn out a barrel far too soon, and may seem horribly "inefficient", but that .300 Wthby. is going to give you the best downrange performance.

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Now if you expand your criteria a bit and come up with a metric of what other factors appeal to you besides raw velocity and energy, the answer changes. What will this gun DO? Is it really a "long-range" gun? What is it shooting at, at long range? Targets? Deer? Enemies? How much energy does the bullet need to be carrying, at what range?

Sam1911's post makes a lot of sense. The default answer is 308. And it is a good choice in shorter barrels. My personal minimum is 20" though. I've had them shorter and never noticed any real advantages as to portability.

But while the 308 loses less from a short barrel, I have 20" 30-06's that are still faster than 24" 308's. The 30-06 loses more of its velocity in shorter barrels , but since it starts with more, it still ends up faster from shorter barrels. Never tried a 300 mag that short, but would be surprsed if that trend were not the same.

What if you kept the cartridge length fixed and let the bore be the variable, ie instead of comparing .300 weatherby to .30 carbine you'd compare .308 winchester to .358 winchester.

The extra barrel volume for the .358 should facilitate the burning of the powder.

If you'd chrono the MV of a .358 and a .308 from 20" barrels and then the same loads from 14" barrels then I'd imagine that the .358 would keep a larger portion of it's velocity. This phenomenom, if it exists, would not be as prominent over all of the possible barrel length spectrum, as it depends on the optimal barrel lengths (being functions of barrel volume among other things) of the calibres.

Basically, for each inch you cut off a .308 you will lose more barrel volume than with a .358. If the optimal barrel length primarily is a function of barrel volume then the optimal barrel length is shorter with a .358 than with a .308. This would mean that for each inch you cut off a .358 you would lose a smaller portion of the optimal barrel length and this should result in a smaller velocity decrease from the optimal muzzle velocity (ie maximum use of expanding gasses optimized in relation to the friction between the bullet and the barrel).

So, without any testing I'd say that if the original question could be phrased as "Which cartridge with a COAL comparable to that of the .308 winchester retains the largest portion of it's optimal muzzle velocity as the barrel length is decreased?", then I would guesstimate something that has a large barrel volume per length of barrel.

The .358 is thus better suited for a short barrel than the .243.

I'm tired and might be completely wrong but at least it's an answer.

The larger bore size question certainly does change the dynamic. But you still have to answer "what for?" You can blow the cartridge out nearly straight-walled and stuff a .45 cal bullet in it. That would give you a cartridge with a lot of momentum. (Though not as much energy!) But the trajectory might not make you happy at longer ranges.

So the pure "how much velocity loss per inch of barrel" question might be somewhat moot.

Sam1911 said:

So the pure "how much velocity loss per inch of barrel" question might be somewhat moot.

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Indeed.

I like the .308 for all of my hunting. Would have preferred the 7mm-08 if that would have been the military standard back in the fifties as I mainly use 165gr bullets anyway but the .308 is fine.

I would say the .308. I have never seen there to be much difference in terminal performance between a 24" or 16" barrel. The military has started using 16" heavy barrels with suppressors for many semiautomatic sniper rifles. The few less inches are necessary to add the suppressor and still have a wieldable gun, and I have not seen any drop in performance. But WOW, is it would without the can on it!

The question you're asking is difficult to answer because there is no hard fast answer. The question can only really be answered in relative terms.

My stock Remington SPS Tactical with a 20" barrel clocked my (then) 100 yard accuracy load, which was a 168gr SMK over 42gr of RL15 in Winchester brass and FGGM primer, at 2400 fps, which is really slow.

I then had that action re-barreled with a 22" Krieger barrel and I picked up about 100fps, but at least some, if not most, of that was by virtue of the tighter chamber and shorter throat. Since then, I've had a second rifle built, again using a Krieger barrel using the same chamber reamer, but I went 26" on that build. With the same load I get just over 2600 fps.

So, in my example, I went from about 2400fps in a 20" stock barrel to just over 2600 fps with the 26" barrel with the custom cut chamber. I had the chamber cut so that a 168gr SMK will be 10/1000ths in the lands when loaded to spec OAL.


EDIT: I went and checked my records and I'm getting just over 2700 fps with the 26" barrel.

The only difference in fast vs. slow powders in a short barrel is how much muzzle flash and still-burning powder you get with the slower stuff. No velocity difference between the two, to amount to anything.

The .308, I've read, was the first computer-aided design. It was intended to get near-'06 velocities from barrels around 20" in length, vs. the then-common 24" '06 barrel. Yeah, it does, but at 55,000 psi vs around 50,000 for the '06.

Back in the Great Used To Be, the factories' advertised velocities were from 26" barrels. Periodically, the American Rifleman's "Dope Bag" or somebody at a gunzine would do the "cut one inch at a time" and chronograph.

Generally, such as the '06 lost about 75 ft/sec/inch. Magnums, about 100 ft/sec/inch. Reportedly, the .308 only loses some 40 or 50 ft/sec/inch.

Recall that the common powders were IMR, such as 4064, etc., and not the ball powders or other, newer chemistry.

curious though as to what barrel length the velocity increase (as you add more inches) suddenly slows down... what i mean is.. if you have a REALLY short barrel (for the sake of arguement) theres a fairly substantial increase in velocity every couple inches.. but where does this increase drop off?.. and what kind of velocities do you tend to find in 16, 18, and 20 inch barrels?

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The manufacturers did not arrive at the standard length barrels by accident. 30-06, and 270 rounds are typically 22-24", most magnum rounds are 24-26". A 308 gets it's optimum velocity somewhere between 20-22". You will still see gains in velocity if you go longer than 22", but the gains will be in smaller and smaller increments as you go longer. For long range target shooters every bit of velocity at 1,000 yards helps. For most hunters shooting at 300 yards or less 200 fps either way is usually not a concern.

The velocity difference between 20" and 22 is usually neglible. In fact some rifles just plain shoot the same ammo 100 fps or more faster than another gun with the same length barrel. I've seen individual guns with 20" barrels shoot the same ammo faster than another gun with a 22" barrel. Once you drop below 20" in a 308 the difference starts to become noticeable. For each inch you cut shorter, the velocity drops in larger and larger chunks. These are averages. There are tons of folks who have chronographed loads with a long barrel, cut the barrel and chronographed it again and again as they go and published the results. You will see a few examples that don't fit the pattern, but look at enough and a trend shows up. You have to decide how much you are willing to give up. For me 20" is as short as i want to go. 24" is as long as I need. For most of my guns, 308, 30-06 a 22" barrel is the perfect compromise. My 300 WSM has a 24" barrel.

Google "velocity and barrel length". There is a lot to read.

http://www.tacticaloperations.com/SWATbarrel/

This is one of the more informative articles.

is this going to be an issue thatll come down to selection of faster powders for greater efficiency in shorter barrels?

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Go back and read post 3 again.

"Efficiency" of faster powders is really a myth. The best (vel./energy) performance will be with the same slow powders that give you the best results with a 26" tube.

You can make loads that do "enough" and do so accurately, and which are a little less unlpleasant to shoot out of a short barrel, but they're still going to be outclassed by whatever your most "magnum" load is, regardless of barrel length.

seems i shouldnt take much of a performance hit on a 16 or 18 barrel vs a 20+.. atleast not enough to worry about it

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And that's really kind of the take-home message. Figure out what velocity you "need" to do what you're trying to do. Deer don't stop a bullet and calculate whether it is going 2,400 fps or 2,600 fps before they decide to fall over dead. Targets don't care either. Pick your rifle and a reasonable chambering for it that is whatever combination of pleasant to fire, cheap to feed, super accurate, versatile, & whatever else that appeals to you. Then chrono what velocity you get with your most accurate load in your gun. Then figure out your dope and write your ballistic chart based on that velocity.

Velocity doesn't kill anything, and it only has an arms-length relationship with the terminal capabilities of your round. Unless you're building a match rifle and have to keep your bullet from going trans-sonic out past a certain range, it just isn't that important.

One other thing. Art and I have had a friendly disagreement on for a while. I've been researching this for years, and shot a lot of loads over a chronograph with barrels ranging from 16"-26". I've never noticed any velocity loss anywhere near the numbers he is quoting. Never found anyone else who did and reported it. The largest loss of velocity I can document is from a guy who cut a 300 mag down to 22" from 24". He lost 70 fps, or about 35 fps/inch.

I see huge velocity differences between various guns with equal length barrels though. My favorite 30-06/150 gr load gives me 3025 fps from one of my 22" guns, only 3045 in another 24" gun, but from other 22" guns ranges from 3015-2890.

This is what makes it hard to predict. If you only look at limited data you could conclude that a 30-06 only lost 10 fps/inch, or 77fps/inch depending on which gun you looked at.

The only methods that have any credibility are the ones where guys start with a long barrel, chronograph loads, cut the barrel and repeat. Every test i've seen on a 308 shows an average of about 25 fps/inch from 26" down to 16". You will see large drops at some intervals, and very small drops at others, but around 250-280 fps total in the 10" loss.

Here is a good read of several rifles that were cut from 27" down to 22". Calibers include 22-250, 270, 300 win mag, 338 win mag and a few others. Most lost around 120 fps or so with the 5" shorter barrel. Or about 25 fps/inch on average.

That is the number I tend to see the most as long as you keep at least 20-22" of barrel. Below that and the numbers get bigger.

http://www.longrangehunting.com/forums/f19/short-barrel-magnum-velocity-19346/

"Efficiency" of faster powders is really a myth. The best (vel./energy) performance will be with the same slow powders that give you the best results with a 26" tube.

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This is what I've found too. I get faster speeds in all barrel lengths with the same powders. My 20" barrels shoot fastest with the same loads that are the fastest in the 24" barrels.

Axxxel touched on something the ballisticians call Expansion Ratio.
How much room is in the barrel for the powder gas to expand into and drive the bullet?
You would gain SLIGHTLY in short barrel performance by going to something like .358 Win on the basic case. Smaller calibers on that chamber are going the wrong way.

But the .308 itself was designed for a 22" barrel and all the tackytickle brags talk about shooting at extreme ranges with 18" barrels and such.

Leave well enough alone.

I think you really can't beat the .280 British round.


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Or .243. Or 7mm-08, or... They're all about the same. Anyone who trys to convince you any of the mid-range rifle cartridges is substantively better than the others is selling something.

The 7-08 wants a longer barrel than the .308 for optimum performance and the .243 wants a longer barrel still. The deal is the ratio of bore diameter to case capacity. The .243 cartridge is about the largest capacity that you efficiently use with the 6mm bore and as such it wants a longer barrel. For the 7mm, the capacity to bore ratio reaches its practical max in the 7mm Rem Mag/7WSM range. The 7-08 is obviously about 33% lower in case capacity and will work in a shorter barrel. The .308 is really nowhere near the max efficient case capacity and will work well in a relatively short barrel.

Expansion ratio was hinted at earlier. Expansion ratio is basically how fast the volume behind the bullet increases once the powder starts pushing the bullet down the bore and it determines the optimal powder burn rate for a given cartridge and bullet weight. Barrel length had nothing to do with powder selection. The "perfect powder" for a given cartridge will reach peak pressure and sustain a high pressure as long as possible. If the powder burns too fast, the pressure will peak quickly with a small powder charge but cannot create the gas volume to sustain the pressure for any duration. If the powder is too slow, you'll fill the case before you hit peak pressure or pressure won't build to a point where the powder burns efficiently.

What happens with a small bore and a large case is that you end up using a powder on the slow end of the spectrum and the pressure stay fairly high until the bullet leaves the bore. The higher the sustained pressure, the more velocity is lost with a reduction in barrel length. With a larger expansion ratio, the pressure drops off more quickly after the peak and less pressure is lost when reducing the barrel length.

It all boils down to powder, but you're not choosing the powder based on barrel length. Rather allowable/optimal barrel length is determined by the optimal powder range for a given cartridge/bullet weight combination. If you want to shoot heavy bullets in an overbore cartridge, you use a slow powder and the velocity delta is large for a barrel length delta. Conversely if you shoot a cartridge with a larger bore compared to case capacity, the correct powder range is faster and the velocity delta for a barrel length delta is lower.

The larger bore size question certainly does change the dynamic. But you still have to answer "what for?" You can blow the cartridge out nearly straight-walled and stuff a .45 cal bullet in it. That would give you a cartridge with a lot of momentum. (Though not as much energy!) But the trajectory might not make you happy at longer ranges.

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Just curious; wouldn't such a round (sounds like a rimless 45-70 or something; interesting idea) have a more efficient energy transfer of powder to bullet? You get the same pressure acting on a larger face (bullet diameter) for a longer time (heavier bullet)? Once you get the muzzle speed up to where it's still above supersonic when it hits its intended max effective range (to get hydro shock, or whatever it's called), do you really gain much (besides trajectory) simply by going faster?

I suppose a sabot is the "best of both" in that you get more efficient energy transfer, and super speed (if that matters). That'd be a slick way to get widely varied performance out of the same gun without changing anything; figure out how to get a finned sabot-load (for stability) to cycle the same action as a heavy full-caliber slug

TCB